Asphalt shingles are composed of: a base material, either organic felt or glass-fiber mat, that provides support for the weather-resistant components and gives a shingle strength; asphalt and fillers; and surfacing material, generally in the form of mineral granules, that provides protection from impact and UV degradation and improves fire resistance.
The most common form of asphalt shingles are strip shingles . They are rectangular, the most prevalent size being 12 inches wide by 36 inches long. Metric shingles are 13 1/4 inches by 39 3/8 inches. Strip shingles most frequently have three tabs that are exposed along the length of the shingle for visual effect and are called 3 tab strip shingles.
Shingles may be produced in a single layer or two or more layers. The latter generally are known aslaminated strip shingles , or architectural shingles, and they have a three dimensional appearance.
Both 3-tab asphalt shingles and laminated asphalt shingles contain a strip of factory applied adhesive that is activated by the sun's heat after installation and seals each shingle to the next course. The seal strip also provides much of a shingle's resistance to wind uplift. Shingles with factory-applied adhesive have a strip of clear polyester film applied to each shingle to prevent the sealing strips from bonding the shingles together when packaged. When the shingles are installed, the self-sealing strips will not align with the plastic film strips and will bond to adjacent shingles. For this reason, the plastic film strips do not have to be removed.